4. Some notation: "abcd/efgh" means "Weigh the coins abcd against
efgh".
"=:" prefixes the action to take if the indicating weighing resulted
in a
balance.
"<:" prefixes the action to take if the right side was heavier
">:" prefixes the action to take if the left side was heavier
"<>:" prefixes an action to take on any imbalance
"(a)" identify a as the counterfeit
"(abc)" the counterfeit is one of abc
"(>abc)" the counterfeit is lighter and one of abc
"(<abc)" the counterfeit is heavier and one of abc
"(<abc,>def)" the counterfeit is one of abcdef. If abc it's lighter,
else
heavier